what type of wood glue?

[triton 496]

Hello to everyone,
Well here is another question pertaining to bonding of teak or mahogany woods. I am building a wooden hatch and would like to glue the corners together, but from what I understand teak is a wood that has natural oil in the grain, so would that inhibit the bonding that glue would provide? As to the bonding agent would a common wood glue do the job or should epoxy be used instead? Any thoughts from experience would be greatly appreciated. Tanks, Al.

[Hirilondë]

Epoxy is unequivocally the best choice. If you clean the mating surfaces with acetone just prior to the glue up there should be no problem. Yes, teak is naturally oily. That is why it survives so long in the marine environment. But if it is cleaned with a solvent just prior to application, and acetone is the best choice, then epoxy, varnish, paint, or what ever will stick just fine.

Because so many have tried making glued joints without cleaning and have therefore had the joint fail, teak joinery now has an undue reputation for being difficult or even impossible to glue.

[okawbow]

Mahagony glues well with titebond 2 and 3. Some epoxies are better than others for gluing oily woods like teak. Be carefull with clamping when using epoxy. Don't use too much pressure, and if you apply pressure, and have to release it to re-align, then you need to re-apply the glue, or you will have a starved glue joint. The better the fit, the stronger the joint.

[Duncan]

I have heard that resorcinol could be a better choice for critical applications, like gluing up a spruce mast.
Then I saw a reference to "resorcinol epoxy", so I'm not sure how much difference there is.

As far as gluing the corners of a hatch, though, I'm sure Dave's experience trumps my hearsay ;)
I'd stick screws in each corner, just on general principle ("belt and suspenders").

For what it's worth, here's a detailed article on the subject.

[Tim]

To eliminate confusion:

Resorcinol is not epoxy. Epoxy is not resorcinol.

[Hirilondë]

Resourcinol would be an acceptable choice as well, but few could live with the purple seam. And like Tim noted, it isn't related to epoxy in any way.

I'm not sure what that article proves. Concordias are notorious for delaminating frames. But you have to consider all of the possible reasons, not just blame epoxy. Not the least of the problems with Concordias being that they were planked too tight. Those with steam bent frames had them broken. We can get into a long and detailed debate here and we would still prove nothing just like that article (yes, I read it).

Epoxy has proven itself over and again. It like everything is not perfect, nor is every application of it. If anyone wants a 100% guarantee that their application will last forever then just give up now. I will continue to use epoxy and use care to assure my joints are fit, cleaned and appropriately assembled and clamped.

I see little to nothing to gain by intellectual debate.

[triton 496]

Ok, epoxy seems to be the preferred method for bonding teak and mahogany woods with screw or two thrown in for good measure!
As always I am humbled by the huge amount of seasoned knowledge offered here at this forum and thank you for your time. All the Best, Al

[bcooke]

That 'article' is also Appendix C in Larry Pardey's Book, Details of Classic Boat Construction (a great book). There was some discussion of it here

[Bluenose]

I have heard that resorcinol could be a better choice for critical applications, like gluing up a spruce mast.
Then I saw a reference to "resorcinol epoxy", so I'm not sure how much difference there is.

As far as gluing the corners of a hatch, though, I'm sure Dave's experience trumps my hearsay ;)
I'd stick screws in each corner, just on general principle ("belt and suspenders").

For what it's worth, here's a detailed article on the subject.

Back when bonded joints were replacing bolts and rivets on airplanes we used to call them "chicken" fasteners. Cause we was a'scared of bonded only primary joints. It really made little sense since bonded joints are much stiffer than bolted joints (which often need to move a bit to take the load) so the bolts pretty much go along for the ride unless the bond fails (which is what we were worried about I guess). Also, it wasn't so much that we didn't trust adhesives it was just that it was difficult to lay down a proper (read thin) glue line and then inspect it so you knew you had one. The thickness of the glue line has a major effect on the strength of the joint.

With respect to the quoted article, when I was an Aerospace engineer (and probably still today) epoxy resin was our default choice. Graphite epoxy when we needed strength and fiberglass when we needed lower cost. In all cases we used something called prepreg which is a product which encase the graphite or fiberglass in an exact amount resin to get the proper resin ratio. The reason this important is that allows you to produce very tight tolerance parts. With all do respect to the "well known and respected yacht builders" they would be building to a different set of tolerances. This could cause a situation where the epoxy is required to be a joint filler in addition to being a bonding agent. There is a big difference between a adhesive failure and a joint failure. Parts of this article seem to blame the adhesive while claiming the builder is qualified. If a builder incorporates an epoxy joint and it fails they are responsible. Since epoxy is more than capable to make graphite composites, which are far stronger than anything on a boat, then any failure is due to improper design or assembly.

In my perfect world it would be bolts (not screws) in any tension or peal applications and glue in shear or torsion. And, this is really going to get me in trouble, screws in fiberglass really seem wrong to me.

Bill

[Hirilondë]

In my perfect world it would be bolts (not screws) in any tension or peal applications and glue in shear or torsion.

In situations where loads are high and/or failure is catastrophic I would agree. Some applications have lesser loads, and failure is merely a nuisance. Epoxy is used because it is most likely sufficient and it looks good to avoid fasteners and their cover ups (bungs, etc.).

There is a big difference between a adhesive failure and a joint failure. Parts of this article seem to blame the adhesive while claiming the builder is qualified. If a builder incorporates an epoxy joint and it fails they are responsible. Since epoxy is more than capable to make graphite composites, which are far stronger than anything on a boat, then any failure is due to improper design or assembly.

I believe you are quite right.

[boatsnh]

I used teak & epoxy to remake both the cabin hatches on "IRIS". dimensions are about 22x24 inches. I did wipe with acetone & did not use any screws at all. Bought a dado blade kit for the table saw and made finger jointed corners (not dovetailed). The finger joints were cut so there was enought room to keep epoxy in the joint so they were not glue starved. Lap joints would also work pretty good too, but have less surface area for the glue to "bite" into. .....Epoxied frames look nice, and no fasteners/bungs in the corners to worry about. For the top I used 1/2 inch acrylic in a "bronze" tint that matches the color of the teak - I have grown to like the color a lot. Matches the teak color & It keeps the cabin bright, but not blindingly so & it allows you to see out, but is pretty hard to see in. Nice for a little privacy with folks walking around on deck, or at a dock. I got the 1/2 acrylic idea from Shannon Yachts - that's what they used when they fabricated teak hatches for their boats, although theirs were translucent white. You can google shannon and see some examples. I also
ran the acrylic out to the edge of the hatch & rounded & polished the acrylic. Easy to finish & no issues with sealing from the weather. Good luck!